The Corridor Test: Finding Mobile Dead Spots in Your UK Office Before You Blame the Network

There is a particular kind of office frustration that starts with someone standing by the window, holding their phone at arm's length, and saying: “It works fine out here.” Meanwhile, the back office, the stockroom, and the meeting room with the thick old walls are where calls go to die. It is tempting to blame the network, switch provider, or sign everyone up to a shiny new mobile deal. But indoor mobile coverage is often a building problem before it is a contract problem.

If your team is struggling to take calls at their desks, the sensible first step is not a sales call. It is a short, structured audit of where the signal actually fails. Think of it as the corridor test: a practical sweep of your premises, done with the phones your staff already use, before anyone reaches for a new SIM or an amplifier from a marketplace listing.

Start with the phones in people’s pockets

The quickest way to find dead spots is to use the handsets already on the desks. Ask staff on different networks — EE, O2, Vodafone, Three, and any smaller providers riding on those networks — to walk the same route through the building. Include the front desk, the main desk cluster, the back office, stairwells, the kitchen, the meeting rooms, the lift lobby, and anywhere deliveries or warehouse work happens. If you have a basement, test it. If you have a room with a suspicious amount of tinfoil-grade insulation, test that too.

Signal bars are a crude guide. A phone showing two bars may still drop a call, while one bar in a quiet spot may handle a short conversation. The useful tests are real ones: make a two-minute call, send a file, load a webpage, and try a video call if that is how the team works. Do it at different times of day. A site that feels fine at 9am can fall over at 4pm when the nearby business park empties its staff onto the same mast.

Keep a simple spreadsheet. Note the room, the network, the handset, what failed, and when. Ask staff to jot down dropped calls for a week. That log is worth far more than a vague memory of “the signal being rubbish near accounts payable”.

Treat coverage checkers as a starting point, not a verdict

Ofcom’s mobile coverage checker is a useful first look. Pop in your postcode and you will get an indication of outdoor coverage by operator and technology. Operator maps can add a bit more detail. But read them with care: they are predictions, not promises about the inside of your building. A postcode can look well served while your particular office sits behind a thick wall, below street level, or in the shadow of a larger building.

Use the checker to narrow things down. If one network looks stronger outdoors, ask a staff member on that network to test indoors. If all networks look similar outdoors but only one works near the fire exit, you have learned something useful. The point is not to crown a winning network from a map. It is to build a picture of what happens in the places where your team actually works.

Wi-Fi calling is helpful, but not a magic wand

Wi-Fi calling can turn a patchy indoor mobile signal into a workable setup, provided your broadband is solid and your handsets and network support it. Most recent iPhones and Android phones can do it, and the major UK networks offer it, but the details vary. Enable it, test it, and make sure staff know when it is active. A call that starts on Wi-Fi and hands over to mobile — or the other way round — is not always seamless.

There are caveats. Guest Wi-Fi may block the necessary traffic. A congested office network can make voice calls sound worse than the mobile signal ever did. And while Wi-Fi calling supports emergency calls, location information may not be as precise as a traditional fixed line, so it is not a reason to rip out every desk phone without a wider plan. If your broadband is the weak link, Wi-Fi calling simply moves the problem indoors.

Legal boosters exist — dodgy repeaters do not belong in your comms cupboard

You may have heard that signal boosters are illegal in the UK. The fuller answer is that certain mobile repeaters can be used legally if they meet Ofcom’s licence-exemption conditions and are properly supplied. The practical route is to talk to your mobile operator or a reputable installer, and to check that any equipment is compliant and CE marked. What you should not do is buy a cheap amplifier from an online marketplace, stick it on the wall, and hope. Poorly designed repeaters can interfere with the network, affect other people’s calls, and land you in bother.

If you rent or share a building, involve the landlord early. External antennas, cabling, drilling, and anything fixed to the fabric of the building may need consent. Listed buildings and conservation areas can add another layer. A shared office may already have a building-wide system, or may have rules about what tenants can install. Get permission in writing before anyone gets handy with a drill.

When the real answer is a fixed line or VoIP backup

Sometimes the audit shows that indoor mobile coverage is genuinely poor and unlikely to be fixed quickly. That is not a failure. It is useful information. If your team needs reliable incoming calls, a fixed-line or VoIP desk phone — or a softphone on the office network — can take the pressure off mobile signal entirely. Mobile-only working is fine when coverage is good. It is a nervy bet when the back office is a black spot and the only place to take a call is standing by the kettle.

This is also where Eden Telecoms would gently point out that “mobile only” is a strategy, not a default. If you are reviewing a mobile contract, do the corridor test first. If the problem is indoors, a new tariff may not fix it. A sensible backup — VoIP on a reliable connection, with a proper business number — often costs less than a doomed attempt to boost a signal that was never there.

Start with a walk around the building, a notebook, and the phones your staff already have. It is a small exercise. It can save a surprisingly large amount of money, and an even larger amount of corridor shouting.